Prostaglandin F and E synthesis by specific tissue components of the brook trout (Salvelinus fontinalis) ovary

The synthesis of prostaglandins (PGs) by several tissue components of brook trout (Salvelinus fontinalis) ovaries was investigated using radiolabeled precursor incorporation and radioimmunoassays for PGE and PGF. PGE2 and PGF2α were synthesized from 14C arachidonic acid (AA) by the follicle walls of mature oocytes. Synthesis was significantly greater in follicles taken postovulation as compared to those sampled prior to germinal vesicle breakdown. However, the most extensive synthesis of PGs occurred with tissue outside of the mature follicles (i.e., extrafollicular[EF]). When incubated with AA, the predominant primary PG produced by this tissue was PGE2. EF tissue could be separated microscopically into two major fractions—immature follicles and stromal tissue. When these tissue fractions were incubated separately with AA the stromal fraction retained the ability to produce PGE2, while the immature follicles increased synthesis of PGF2α. 14C‐Eicosatrienoic acid was converted to PGE1 and PGF1α by EF tissue but in significantly reduced quantities relative to AA. Fatty acid analysis indicated that there were significant quantities of arachidonic, eicosapentaenoic, and docosahexaenoic acids in both follicles and EF tissue, but there was not a significant difference between the two tissues in the absolute amount of arachidonate/mg tissue. In experiments using radioimmunoassays (RIAs), the highest quantities of PGE were measured in incubates containing EF tissue. This supported the results obtained through arachidonic acid incorporation and suggested that this tissue is the primary source of PGE in the brook trout ovary. In contrast, the mature follicules that were undergoing ovulation in vitro produced significant quantities of PGF, whereas the EF tissue production of PGF, measured by RIA, was very low. The results clearly indicate that there are several potential sites for PG synthesis within the trout ovary that differ in their capacity to produce E and F prostaglandins.